1. A program written in ethereum can execute code at a predetermined point in the future, and there is as close to 100% certainty as possible that the code will execute as written (i.e. as long as a single ethereum user remains in the world at that date everybody's code is guaranteed to run exactly as written, even if it involves moving money between accounts.)
2. All computer programs are "open source" not just before a program is launched but also WHILE THE PROGRAM IS RUNNING- Nobody can run any code without having full transparency.
3. Users accounts are provably always in a state of complete anonymity (unless of course they do something to purposely reveal their identity) and can use all programs on the platform in this fully anonymous state.
4. Program authors are forced to explicitly document ahead of time all situations in which their program code might be modified in the future, making it much harder to have the "screw your user after they've committed to your platform" business model that's so popular among startups these days.
Those are just some of the properties of ethereum that come to mind.